Category Archives: Seasons

What is La Niña and the impact on Wisconsin’s coming winter weather?

La Niña refers to a departure from normal in the sea-surface temperature across much of the eastern tropical Pacific Ocean.

The water temperatures off the west coast of South America are typically 60 to 70 degrees. During a La Niña these waters get as much as 7 degrees colder than normal. La Niña conditions recur every few years and last nine to 12 months, though some events have lingered for as many as two years. This cooling results from a strengthening of the winds over the tropical Pacific and its interaction with the underlying ocean waters. Continue reading

Category: Climate, Meteorology, Seasons

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How does frost form?

Frost on objects is just water vapor in the air that has deposited itself as ice onto a surface. Frost forms on objects close to the ground, such as blades of grass.

At night, a blade of grass loses energy by emitting radiation (a non-lethal kind) while it gains energy by absorbing the energy emitted from surrounding objects. Under clear nighttime skies, objects near the ground emit more radiation than they receive from the sky, and so a blade of grass cools as its energy losses are greater than its energy gains. If the temperature of a grass blade gets cold enough and there is sufficient water vapor in the environment, frost will form on the grass. Continue reading

Category: Meteorology, Seasons

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How is the Artic Sea ice situation?

The sea ice cover in the Arctic Ocean is one of the key components of our climate system.

The brightness of the sea ice reflects more solar energy to space than open water. Global warming is amplified in the Arctic as the ice cover decreases. This is referred to as the ice-albedo feedback. Continue reading

Category: Climate, Meteorology, Seasons

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When does autumn begin?

The changes are subtle but apparent to the keen observer at this time of year — the first changes of color on trees, the earlier sunset and the rapid temperature drop that follows.

Summer is ending and fall is taking its place. This fact is formalized at 2:20 p.m. Wednesday when the autumnal equinox occurs. Continue reading

Category: Climate, Meteorology, Seasons

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Are we near the end of hurricane season?

It has been a particularly impactful hurricane season in the Atlantic thus far. As of Sunday, there have been 12 named storms — Larry being the current storm of interest.

Hurricane Ida was a very impactful storm, and tens of thousands remain without power in the metro New Orleans area. The so-called remnants of Ida also walloped the northeastern U.S. on Wednesday and Thursday, resulting in dozens of deaths and widespread flooding in many states not usually so affected. Continue reading

Category: Climate, Seasons, Tropical

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